A typical surgical tourniquet system of the prior art includes a tourniquet cuff for encircling a patient's limb at a desired location and a tourniquet instrument that includes flexible instrument tubing for connecting to the tourniquet cuff. The tourniquet cuff typically includes an inflatable portion, and the inflatable portion of the cuff is typically connected through a cuff port having a port connector to the flexible instrument tubing of the tourniquet instrument, thereby establishing a pneumatic passageway from the tourniquet instrument through the instrument tubing and the cuff port into the inflatable portion of the cuff. In some prior-art systems, the tourniquet instrument includes a pressure transducer to sense the pressure of gas at the instrument end of the pneumatic passageway and to enable the sensed pressure to be displayed for surgical staff. Some prior-art tourniquet instruments include a pressure regulator to increase and decrease the pressure of gas in the pneumatic passageway, and to maintain the pressure in the inflatable portion of the cuff at a pressure above a minimum pressure required to stop arterial blood flow past the cuff during a time period suitably long for the performance of a surgical procedure. Many types of pneumatic surgical tourniquet systems, including tourniquet cuffs and tourniquet instruments, have been described in the prior art, such as those described by McEwen in U.S. Pat. Nos. 4,469,099, 4,479,494, 5,439,477 and by McEwen and Jameson in U.S. Pat. Nos. 5,556,415 and 5,855,589.
Some tourniquet cuffs of the prior art have only a single port for connection to the tourniquet instrument and thus establish only a single pneumatic passageway between a tourniquet instrument and the inflatable portion of such cuffs. The pressure in the inflatable portion of such single-port tourniquet cuffs must be sensed indirectly from the tourniquet instrument, through the same pneumatic passageway that is used by the tourniquet instrument to increase, decrease and regulate cuff pressure during surgery. The flow resistance of the pneumatic passageway affects the accuracy and speed of regulation of pressure within the inflatable portion of such single-port tourniquet cuffs as well as the accuracy of the indirectly sensed tourniquet cuff pressure.
Other tourniquet cuffs of the prior art have dual ports to establish two separate pneumatic passageways between the tourniquet instrument and the inflatable portion of the cuff, to achieve increased safety and performance by enabling the tourniquet instrument to provide surgical staff with a more accurate indication of cuff pressure and by enabling the tourniquet instrument to increase the speed and accuracy of cuff pressure regulation. Representative dual-port tourniquet cuffs of the prior are described in U.S. Pat. Nos. 4,635,635, 5,454,831, 5,439,477, 5,741,295 and 5,649,954. In one dual-port tourniquet system of the prior art, described in U.S. Pat. No. 4,469,099, the pneumatic pressure regulation elements within the tourniquet instrument communicate with the inflatable portion of the tourniquet cuff through one pneumatic passageway of the tourniquet cuff, and a pressure sensor within the tourniquet instrument communicates pneumatically with the inflatable portion of the cuff through a separate pneumatic passageway of the cuff.
With both single and dual-port tourniquet systems, the speed and accuracy of pressure regulation and indication are improved if flow restrictions in the pneumatic passageway are minimized. Typical port connectors of the prior art have a male barbed connection portion which fits inside the pneumatic passageway of the port, creating a region of reduced pneumatic flow area and increasing flow resistance between the cuff and the tourniquet instrument.
One hazard associated with all pneumatic tourniquet cuffs of the prior art is the obstruction of the pneumatic passageway within the cuff. For example, in a single-port tourniquet cuff, a complete obstruction within the pneumatic passageway may allow the actual pressure in the inflatable portion of the cuff to decrease substantially below the desired tourniquet pressure to a level where the cuff may be completely depressurized, or to increase substantially above the desired tourniquet pressure, without any indication to the surgical staff. In effect, the monitoring and regulation of cuff pressure by a prior-art tourniquet instrument stops at the location of the obstruction. As another example, a complete obstruction within a region of the inflatable portion of the cuff may isolate all or part of the inflatable portion and thus may prevent the pressure throughout the entire inflatable portion of the cuff from being sensed and regulated near the desired pressure by the tourniquet instrument. Any isolated region may be hazardous, either by permitting arterial blood to flow into the limb past a region of lower cuff pressure or by requiring surgical staff to set the tourniquet instrument to an unnecessarily high pressure to stop blood flow past the cuff. Also, any complete obstruction of the pneumatic passageway within a tourniquet cuff of the prior art may render ineffective any audio-visual safety alarms of a connected prior-art tourniquet instrument intended to warn of hazardous over-pressurization or under-pressurization of the cuff, such as the safety alarms described by McEwen in U.S. Pat. No. 4,469,099.
Another hazard associated with tourniquet cuffs of the prior art is partial obstruction of the pneumatic passageway. A partial obstruction of the pneumatic passageway at the port connector, or elsewhere within the port or inflatable portion of a prior-art cuff may increase the pneumatic flow resistance at the partial obstruction, and thus may affect the ability of a connected tourniquet instrument to rapidly and accurately regulate pressure past the partial obstruction and throughout the inflatable portion of the tourniquet cuff. Increased flow resistance from a partial obstruction may also reduce the ability of a connected tourniquet instrument to accurately and rapidly indicate changes of the pressure in the tourniquet cuff to surgical staff. Further, a partial obstruction of the pneumatic passageway within a region of the inflatable portion of the cuff may affect the ability of the tourniquet instrument to uniformly regulate pressure throughout the entire inflatable portion of the cuff.
In addition to the hazards of complete and partial obstructions that may affect the integrity of the pneumatic passageway, another hazard associated with prior-art cuffs is the interruption of the passageway due to unanticipated detachment of the port connector from the tourniquet instrument, or detachment of the port connector from the port, thus separating the inflatable portion of the tourniquet cuff from the tourniquet instrument. A related hazard is a leak at the port connector that is sufficiently large to prevent a connected tourniquet instrument from maintaining cuff pressure near the desired pressure. Such a large leak may result, for example, from deterioration or deformation of the connector of a single-use disposable tourniquet cuff as a result of reprocessing and reuse of the disposable tourniquet cuff in multiple surgical procedures in a manner neither intended nor anticipated by the manufacturer.
Many disposable tourniquet cuffs of the prior art are designed to be used in only one single surgical procedure and then discarded. Many such disposable tourniquet cuffs are sterilized at time of manufacture and supplied to users as sterile products, because such cuffs are typically intended to be suitable for use within sterile surgical fields. As a result, the design characteristics of such prior-art cuffs are intended to allow them to be applied and used safely and reliably within a sterile surgical field during one surgical procedure, and to be discarded cost-effectively after that procedure. For example, some disposable tourniquet cuffs of the prior art have a port that includes a very flexible thermoplastic tubing portion having a length sufficient to allow a user to easily bend the port away from the surgical site and position the port connector beyond the sterile surgical field. Although such long and flexible port tubing facilitates connection of the port to non-sterile instrument tubing away from the sterile surgical field, it may also increase the possibility of partial or complete obstruction of the pneumatic passageway within the port, for example by accidental kinking, bending, or pinching of the tubing. The various materials and components from which such prior-art disposable tourniquet cuffs are assembled are chosen to be sufficiently inexpensive to allow the cuff to be economically discarded after a single use, and also to be capable of sterilization by exposure to a specific sterilizing agent within a specific sterilizing process determined by the manufacturer, with no significant deterioration or change of properties that would impair the safety or performance of the cuffs after such sterilization.
Efforts have been made to reprocess and reuse tourniquet cuffs of the prior art that were originally supplied by their manufacturers as sterile, single-use products. Reprocessing efforts typically involve saving rather than discarding a disposable tourniquet cuff after surgery, visually examining the cuff to identify any obvious deterioration that might suggest reprocessing is not appropriate, attempting to remove any blood and other surgical debris by washing the cuffs with water combined with any of a variety of detergents or other cleaning liquids, in some cases conducting some functional tests of the cuff, re-packaging the cuff and then sterilizing the re-packaged cuff by exposing it to a sterilization agent within a sterilization process that may be different from that determined by the original manufacturer to be safe and effective. Reprocessing of disposable tourniquet cuffs may be carried out within hospitals or surgery centers or by third-party reprocessors, and the quality and methods of reprocessing are highly variable.
Reprocessing, cleaning and re-sterilizing of disposable tourniquet cuffs may result in hazards for the surgical patients on whom such cuffs are subsequently used. The hazard arises from the use of any of a variety of chemical or physical agents that are attendant with the reprocessing, cleaning or re-sterilizing processes. For example, exposure of a cuff to liquids during cleaning may allow the liquids to enter the pneumatic passageway of the cuff, where they may remain to partially or complete obstruct the pneumatic passageway of the cuff within the port or inflatable portion. Water remaining within the pneumatic passageway after cleaning may subsequently react chemically with ethylene oxide, a sterilizing agent commonly used in reprocessing, to form ethylene glycol, a sticky substance that may completely or partially block the pneumatic passageway. Exposure of prior-art cuffs to sterilizing agents different than the sterilizing agent employed at the time of manufacture may produce a change and deterioration in the properties of some cuff materials and components, for example due to a chemical reaction or exposure to radiation. Exposure of a prior-art cuff containing flexible thermoplastic materials to an elevated temperature during cleaning or sterilization by known prior-art processes may soften thermoplastic materials and components, increasing the likelihood of hazardous deformation of some components. For example, an elevated temperature during reprocessing may result in substantial deformation of the thermoplastic stiffener included in some prior-art cuffs, thus impairing the application of pressure by such a cuff to an underlying limb upon subsequent use in surgery. Also, an elevated temperature during reprocessing may deform the thermoplastic connectors of some prior-art cuffs, or may weaken the retention force of typical thermoplastic barb-type port connectors, so that such connectors cannot establish or reliably maintain a gas-tight passageway between the tourniquet cuff and tourniquet instrument upon reuse. An elevated temperature associated with cleaning or re-sterilization increases the likelihood that the pneumatic passageway within the cuff may become partially or completely obstructed, as described above, as a result of such reprocessing. Repeated cleaning, re-sterilization and reuse of a disposable tourniquet cuff in multiple surgical procedures may progressively increase the hazard for the surgical patients on whom the cuff is used.
There is a need for a tourniquet cuff that has minimal flow restrictions within its pneumatic passageway under normal operating conditions, that has a substantially reduced likelihood of partial or complete obstructions or interruptions of the pneumatic passageway under foreseeable operating conditions, that can indicate exposure of the cuff to one or more external agents that are capable of affecting the integrity of the pneumatic passageway before use, and that can be manufactured economically. The present invention addresses this need.